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Hydrothermal synthesis of quantum dots dispersed on conjugated polymer as an efficient electrodes for highly stable hybrid supercapacitors
摘要： Hydrothermal synthesis of graphene quantum dots (GQDs) composited with conjugated polymer were investigated the high specific capacitance and cyclic stability of supercapacitor. The situ chemical polymerization method was employed to synthesize the polypyrrole - graphene quantum dots (PPY-GQDs) composite at different concentrations of GQDs. The size, morphology and structural phase of the PPY- GQDs composites was studied by using Transmission Electron Microscope (TEM), Field Emission Scanning Electron Microscope (FESEM), Atomic Force Microscope (AFM) and X-ray diffractometry (XRD) techniques respectively. The optical and electrochemical measurements were carried out by using Ultraviolet-Visible (UV–Vis) Absorption spectroscopy, Photoluminescence Spectroscopy (PL) and electrochemical work station. The cyclic voltammetry (CV) results show enhanced current density and area of CV loop with increasing scan rate and the concentration of GQDs. The Supercapacitor was fabricated by two electrodes owns a high energy density 67.8 Wh/kg and 93 Wh/kg at a power density of 1210 W/kg and 1430 W/kg for PGC1 and PGC3 composites. The highest specific capacitance values 467.32 and 647.54F/g are achieved by PGC1 and PGC3 composite compare to pure PPY. The PPY-GQDs composites achieved excellent cycle stability until the 2000 cycle. Thus, it demonstrates that GQDs is playing a unique and important role in improving the performance of a hybrid supercapacitor device.
关键词： Electrochemical Impedance spectra,Graphene quantum dots,Specific capacitance,Supercapacitors,Polypyrrole
更新于2025-09-23 15:21:01
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Harnessing polymer grafting to control the shape of plasmonic nanoparticles
摘要： Matrix-free polymer grafted nanoparticles (NPs) are single component polymer nanocomposites (PNCs) for which the often reported severe aggregation of the conventional PNCs can be suppressed. For a given particle core, the size and shape of the polymer grafted nanoparticles can be controlled by the molecular weight of the polymer and its grafting density. However, the degree of homogeneity of one-component PNCs depends on the grafted chain molecular weight and grafting density, as well as on the shape of grafted NPs. Surface plasmon resonance enhanced dynamic light scattering from very dilute solutions, yielding both translational and rotational transport coefficients, complemented by UV–Vis extinction spectra, can detect deviations from spheres. Here, we report that poly(isobutylene)-grafted Ag NPs strongly deviate from the spherical shape and are modeled as prolate spheroids. This NP asphericity, due to inhomogeneous grafting, can impact the structure and properties of plasmonic PNCs in the solid state. Thus, characterizing this behavior is a crucial step prior to the formation of one-component PNCs.
关键词： shape control,polymer grafting,dynamic light scattering,UV–Vis extinction spectra,plasmonic nanoparticles
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Performance characterization for bifacial photovoltaic modules
摘要： The performance of bifacial photovoltaic modules were characterized. The optical transmittance was measured for front and back side illumination. The temperature coefficients were obtained in order to predict the real power that can be produced in an installation under operating conditions. The internal quantum efficiency distribution was measured to distinguish recombination activity which occurred at the silicon via two-dimensional LBIC method.
关键词： optical transmittance spectra,temperature coefficient,bifacial perc solar cells,quantum efficiency
更新于2025-09-23 15:21:01
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Prominent radiative contributions from multiply-excited states in laser-produced tin plasma for nanolithography
摘要： Extreme ultraviolet (EUV) lithography is currently entering high-volume manufacturing to enable the continued miniaturization of semiconductor devices. The required EUV light, at 13.5 nm wavelength, is produced in a hot and dense laser-driven tin plasma. The atomic origins of this light are demonstrably poorly understood. Here we calculate detailed tin opacity spectra using the Los Alamos atomic physics suite ATOMIC and validate these calculations with experimental comparisons. Our key finding is that EUV light largely originates from transitions between multiply-excited states, and not from the singly-excited states decaying to the ground state as is the current paradigm. Moreover, we find that transitions between these multiply-excited states also contribute in the same narrow window around 13.5 nm as those originating from singly-excited states, and this striking property holds over a wide range of charge states. We thus reveal the doubly magic behavior of tin and the origins of the EUV light.
关键词： multiply-excited states,tin plasma,EUV lithography,atomic physics,opacity spectra
更新于2025-09-23 15:21:01
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Broadband Ultrashort Pulses in Passively Mode-Locked Fiber Lasers
摘要： Generation of ultrashort pulses with an ultimately broad spectrum in fiber lasers is investigated by using numerical modeling and analytical calculations. It is demonstrated that the spectral width of the generated pulses can be several times larger than the gain bandwidth of the laser active medium.
关键词： passive mode-locking,spectra of pulses,generation dynamics,fiber lasers
更新于2025-09-23 15:21:01
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Luminescence of Phosphate Glasses: P2O5-ZnO-BaF2-K2TeO3-Al2O3-Nb2O5 Doped with Sm3+ Ions for Display and Laser Material
摘要： Luminescent phosphate glasses having the composition 40P2O5-30ZnO-20BaF2-3.8K2TeO3-1.2Al2O3-5Nb2O5 in mol.% doped with 3 9 103 ppm and 4 9 103 ppm Sm2O3 were successfully prepared by a melt-quenching technique. The investigated glasses were characterized by x-ray diffraction, UV–visible–NIR, absorption, emission, and ?uorescence lifetime analysis. The radiative properties were calculated using Judd–Ofelt (J–O) spectral intensity parameters for each of the glasses, which revealed the following trend: X2 > X4 > X6. The J–O intensity parameters were used to evaluate the spontaneous emission properties including branching ratios, transition probabilities, and radiative lifetime. The value of the optical energy band gap was found to decrease with an increase in Sm3+ content, which is explained on the basis of structural changes. The calculated stimulated emission cross-section studied was high, and increased from rSE; at 1.62 lm of glasses 3.81 9 10(cid:2)21 cm2 to 4.38 9 10(cid:2)21 cm2 with increasing Sm3+ ion concentration. The structure of the glasses was investigated by computing Internuclear (cid:3) and ?eld strength F( ) and measurement of Raman spectra.
关键词： refractive index,UV–Vis–NIR,Judd–Ofelt analysis,emission cross-section,Raman spectra,Oxide glasses,density,optical energy gap
更新于2025-09-23 15:21:01
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Luminescence Line Broadening of CdSe Nanoplatelets and Quantum Dots for Application in w-LEDs
摘要： Nanoplatelets (NPLs) of CdSe are an emerging class of luminescent materials, combining tunable and narrow emission bands with high quantum yields. This is promising for application in white light LEDs (w-LEDs) and displays. The origin of the narrow spectral width of exciton emission in core NPL compared to core-shell NPL and quantum dot (QD) emission is not fully understood. Here we investigate and compare temperature dependent emission spectra of core and core-shell CdSe NPLs and QDs. A wide temperature range, 4 to 423 K, is chosen to gain insight in contributions from homogeneous and inhomogeneous broadening and also to extend measurements into a temperature regime that is relevant for operating conditions in w-LEDs (T~423 K). The results show that temperature induced homogeneous broadening does not strongly vary between the various CdSe nanostructures (ΔEhom≈60-80 meV at 423 K) indicating that electron-phonon coupling strengths are similar. Only for the smallest QDs stronger coupling is observed. The origin of the narrow bandwidth reported at 300 K for core CdSe NPLs is attributed to a very narrow inhomogeneous linewidth. At 423 K the spectral width of NPL exciton emission is still superior to that of QDs. A comparison with traditional w-LED phosphors is made to outline advantages (tunability, narrow bandwidth, high efficiency) and disadvantages (color shift, stability issues) of NPLs for application in w-LEDs.
关键词： w-LEDs,Quantum Dots,Temperature dependent emission spectra,CdSe Nanoplatelets,Luminescence
更新于2025-09-23 15:21:01
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Nonresonant Polarized Raman Spectra Calculations of Nitrogen-Doped Single-Walled Carbon Nanotubes: Diameter, Chirality, and Doping Concentration Effects
摘要： Raman spectra of nitrogen-doped single-walled carbon nanotubes are calculated using the spectral moment’s method combined with the bond polarizability model. The influence of the nanotube diameter and chirality is investigated. We also address the important question of the effect of the N-doping concentration, and we propose an equation to estimate the doping concentration from the knowledge of the tube diameter and the frequency of the radial breathing mode.
关键词： spectral moment’s method,Raman spectra,N-doping concentration,nanotube diameter,nitrogen-doped single-walled carbon nanotubes,bond polarizability model,chirality
更新于2025-09-23 15:21:01
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High-resolution cw-cavity ring-down spectroscopy of allowed (??4??+????5)0 and forbidden (??4??+????5)2 bands of C2H2 using external-cavity quantum cascade laser
摘要： In this paper, we measured the absolute line intensities and air broadening coefficients of several rotationally resolved lines in the P and R branches of the allowed (ν4+ν5)0 and forbidden (ν4+ν5)2 vibrational combinational bands of C2H2 at room temperature 296K. These measurements were performed using an external-cavity quantum cascade laser (EC-QCL) operating at 7.5 μm coupled with high-sensitive cavity ring-down spectroscopy (CRDS). Rotational level-dependent pressure-broadening coefficients of the resolved spectral lines of the selected transitions from (ν4+ν5)0 band are reported here. The air broadening coefficients for 5 rotational lines from P-branch of (ν4+ν5)2 band were also obtained first time with better than 3% uncertainty. The vibrational transition dipole moment squared values of the rotational lines and empirical Herman-Wallis coefficients were also quantified from experimental data. Finally, experimentally obtained all spectroscopic parameters were rigorously compared with previous studies. The new experimental data including several spectroscopic parameters will be useful for atmospheric and astrophysics applications.
关键词： Cavity ring-down spectroscopy,Absolute measurement of line intensities and air broadening coefficients,Transition dipole moment,Ro-vibrational allowed and forbidden transition,Quantum cascade laser,Infrared spectra of Acetylene
更新于2025-09-23 15:21:01
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Analysis of the A ??=1 a?? X 3?￡a??0+ transition of PtS observed by intracavity laser spectroscopy with fourier transform detection (ILS-FTS), and computational studies of electronic states of PtS
摘要： The (0,0) and (1,0) vibrational bands of the A U?1 e X 3S?0t transition of PtS have been observed in high resolution absorption measurements recorded using intracavity laser spectroscopy with Fourier transform detection (ILS-FTS). Hyper?ne structure in 195PtS lines was observed in the Q-branches only, due to the interaction of an unknown U?0? state with the f levels of the A U?1 state. The new (0,0) vibrational band has been rotationally analyzed and ?t using PGOPHER. Results from the spectral analysis including deperturbation of the (0,0) band of the A U?1 state are presented. Potential energy curves, spectroscopic constants, and transition dipole moments are presented for L-S and U electronic states with Te < 25,000 cm?1, based on high-level ab initio calculations. Experimentally observed electronic states of PtS are correlated to predicted states.
关键词： Platinum sul?de,PtS,High-resolution electronic spectra of metal-containing radicals,Ro-electronic analysis,ILS-FTS,Perturbation analysis
更新于2025-09-23 15:21:01